This invention relates to sheet metal bending brakes and more particularly to the means for supporting and locking the upper tools used by these brakes.
Bending brakes generally comprise a structure having two opposing toolplates substantially lying in the same vertical plane, and of which one can move vertically. To the facing edges of the toolplates are fixed the means for supporting and locking the bending tools, which are aligned in succession and grouped as a plurality of upper tools and a plurality of lower tools (punch and die respectively).
Said tool support and locking means are fixed to the respective toolplates and are arranged to receive the tool shank such that it can be slid along the longitudinal axis of the toolplate and be locked in the desired position.
When the type of work changes, one or more tools have also to be changed, this being generally done by withdrawing or inserting the tools from or into the support and locking means in a longitudinal direction. Withdrawing, adding or changing a tool is a particularly delicate and even dangerous operation, in particular with regard to the upper tools, which can also be very long and heavy.
For this reason, tool support and locking means have been developed for bending brakes which also enable the tool to be withdrawn vertically, in the brake working direction.
The known means are rather complicated because they have to comprise safety means to prevent any accidental fall of the tool when it is released.
A fixture conforming to the known art, comprising said tool support and locking means, is described in EP 0494714, in which the tool support and locking means comprise a lower channel into which the upper portion of the tool (also known as the shank) is inserted.
The tool can be inserted from below into a seat having the same form as the shank, and locked in position by a plurality of pneumatically operated pistons which enter a longitudinal groove present in the tool shank. Each of said means also has a safety device comprising a lever for operating a peg movable within a hole in the support means which, when the shank has been inserted into the seat in said support and locking means, is maintained elastically inserted in a longitudinal cavity present in one of the vertical walls of said seat.
When a tool, for example one of those which form the upper punch of the brake, is to be changed, the locking pistons are retracted so that the tool remains supported only by the peg.
At this point the tool can be withdrawn in the direction of the toolplate edge, or, by pressing said lever, it can be withdrawn in a vertical direction.
This solution is costly to implement, and in addition the peg present in the safety device is easily damaged during use, so being unable to perform its functions.
An object of the invention is to overcome the aforementioned drawbacks within the framework of a rational, reliable and low-cost solution.
A further object of the invention is to provide tool support and locking means which can be used easily and safely by the operator.
These and further objects are attained by the invention as characterized in the claims.